1. Field of the Invention
This invention relates generally to a liquid level indicator gauge, and more particularly to a portable gauge which can be conveniently and easily clamped onto a liquid storage tank for accurately determining the amount of liquid contained therein.
2. Description of the Prior Art
Liquid storage tanks are used to contain various substances in a wide range of applications. It is usually of interest, and often a necessity, to determine the level of liquid in a storage tank. Many approaches have been developed for determining liquid level. In most instances, the liquid level gauge is permanently installed on the storage tank. However, it is relatively expensive to provide a liquid level gauge in each storage tank when liquid level must be monitored in a plurality of such tanks. Furthermore, most liquid level gauges are not suitable for use as a portable device because of their intricate design, electrical connections, excessive weight, or bulkiness. Such gauges cannot be readily transported from one tank to another without undue risk of damage to the internal workings or delicate, external features of the device.
In some cases, rudimentary means are sufficient to determine liquid level, such as the insertion of a measuring rod or dip stick through an opening in the top of the storage tank. The measuring rod is typically graduated, with markings along its length which are indicative of the level of liquid contained in the tank. One end of the rod is initially placed in abutment against the bottom of the storage tank and the rod is then withdrawn. The liquid level is apprised by simply observing how much of the rod is wetted relative to the liquid level markings. However, various problems arise through the use of such a method to measure liquid depth. For example, certain volatile liquids, such as gasoline, tend to evaporate quickly so that the wetted portion of the rod may not be readily observable, especially in poor light. On the other hand, viscous liquids, such as diesel fuel or crude oil, are stable but are not easily wiped or removed from the measuring rod. Moreover, an accurate liquid level measurement is only possible if the measuring rod is manually aligned in a substantially vertical orientation.
More refined approaches for determining liquid level in a storage tank have been developed which utilize portable measuring devices. Such devices are disclosed in U.S. Pat. No. 3,691,839 to Lasher, and U.S. Pat. No. 4,819,484 to White. Although these devices are transportable, they do not have features which allow them to be easily and securely attached to the storage tank. Moreover, the liquid level reference point for these particular devices is the exterior top surface and interior bottom surface of the storage tank, respectively. However, in certain storage tank applications, such as a railroad tank car, the liquid level reference point is typically the interior top surface of the tank car.
The present invention attempts to remedy the problems and drawbacks of prior liquid level gauges, and provides a portable liquid level indicator gauge which easily and securely clamps onto a railroad tank car to accurately determine the amount of liquid contained therein relative to a predetermined liquid level reference point.